1. Field of the Invention
The invention relates to a dental device and a method for determining the state of an at least partially metal tooth crown or tooth bridge. The invention further relates to a dental reference electrode for the dental device and the method.
2. Discussion of the Background
For a long time, tooth crowns or tooth bridges consisting at least partially of metal were fitted on teeth without the complete removal of any amalgam fillings which may have been present. If amalgam comes into direct contact with, for example, gold crowns or gold bridges, accelerated anodic corrosion of the amalgam can take place. The products of corrosion of the amalgam, for example copper ions, tin ions, silver ions or mercury ions, can have a toxic action on the gum. In some circumstances, so much mercury is released that dangerous mercury allergies and serious disturbances of the central nervous system occur. Mercury ions pass through the bloodstream and the blood/brain barrier into the brain, the critical organ for accumulation of mercury. For this reason, it is advisable to completely remove amalgam which is located underneath an at least partially metal tooth crown, such as a gold crown.
Unfortunately, however, it has not hitherto been possible to detect the presence of amalgam without destroying and dismantling the tooth crown or tooth bridge. Conclusive X-ray pictures cannot be taken because a gold crown provides too much shielding against the X-rays, with the result that no contrast can be obtained for the amalgam which may be present.